Muscarinic receptor regulation of Ca2+ mobilization in a human salivary cell line (original) (raw)

We have studied receptor-mediated Ca 2 + mobilization in an established exocrine epithelial cell line (HSG-PA) derived from a human submandibular gland. These cells possess a single class of high-affinity muscarinic cholinergic receptors identified using [3H]-quinuclidinylbenzilate (Kd = 0.17 + 0.07 nmot/1; B,~x = 37 _+ 2 fmol/mg protein; n = 3). The muscarinic agonist carbachol elicits a concentration dependent increase of [3H]-inositol trisphosphate in HSG-PA cells (100 gmol/1; >2 fold by 30 s). Carbachol also results in a rapid, ~ 5-fold increase in cytosolic [Ca2+]. This response is made up of two components, one arising from the release of intracellular Ca z+ (La 3+ insensitive; independent of extracellular [Ca z +]), the other from the entry ofextracellular Ca-* + (La 3 + sensitive; dependent on extracellular [Ca2+]). These Ca 2+ mobilizing mechanisms are completely blocked by the muscarinic antagonist atropine (10 gmol/l) but unaffected by several voltage-dependent Ca 2+ channel antagonists (verapamil, nifedipine, diltiazem) and by membrane depolarization (incubation in 55 mmol/l KC1). These results demonstrate that HSG-PA cells respond to muscarinfc stimulation by mobilizing Ca 2+ from an intracellular store and via a receptor-operated Ca 2 + entry pathway.